In my life, I have had a poodle, a lab, now, a dachshund and mostly yorkies. But, the one dog that was out of control and totally hard to do anything with was the: Jack Russell Terrier!! I know they are really smart and I liked the idea of teaching them to do the obstacle course. We also have horses and I had seen them at the steeple chases in our area. They have Jack Russell races. So I had to have one!! They require a lot of work! Plus, they get bored very easy so they have to be busy all day! Mine pulled off wall paper from the walls and almost chewed through the entire leg of the dinning room table before I caught her. She lived the rest of her days outside and as it would be, got runned over by a car because she was always jumping the fences, etc.
I think I like Yorkies the most, they are well tempered, yet can be a little aggressive and they are very smart and will listen to training well. The dachshund is pretty good too, although a hound, tame enough to live inside.